Diamond-like carbon (DLC) films have been extensively studied for more than two decades due to their highly attractive properties. These films exhibit unique mechanical, electrical and tribological behavior and thus, possess great potential for applications in tribology. However, the high level of internal stress developed and low thermal stability are the main drawbacks. Synthesis of nitrogen-doped DLC (N-DLC) offers the possibility of overcoming these drawbacks. In the present study, DLC and N-DLC films (with low N content) were deposited on Si substrates using a hybrid plasma-assisted CVD/PVD process. Film characterization in terms of microstructure, composition and chemical state of components was carried out by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Mechanical properties of the films were characterized by microhardness testing. The tribological properties were studied by conducting pin-on-disc experiments. Surface optical profilometry was used to analyze the wear profiles and calculate the Archard wear rates.

TEM and XPS analysis showed that low amounts of N-doping results in the formation of an amorphous structure with the presence of short-ranged diamond-like structure (sp3). N-doped DLC films were found to possess comparable hardness with that of DLC films. They exhibited friction coefficients as low as 0.04 compared to 0.2 for DLC, but maintained comparable Archard wear rates with DLC of the order of 10-7 mm3/Nm. The N-DLC film with 0.73 at. % N exhibited the best tribological behavior. The nanosmooth appearance of the surface, ultralow friction coefficients and low Archard wear rates of N-DLC films obtained with low doping of N in the DLC matrix, show promise for applications such as magnetic hard drives and medical implants.